A wireless mobile communication requires fast mobility and fast data transmission. To this end, an orthogonal frequency division multiplex (OFOM) modem is used in a physical layer. An Inverse Fast Fourier Transform (IFFT)/Fast Fourier Transform (FFT) apparatus is indispensable for the OFDM modem to transmit and receive data.
The IEEE 802 (11a, 16e, etc.) standard adopts the OFDM as a modulation standard and suggests various sizes of the IFFT. Fast wireless communication uses an IEEE 802 (11a, 16e, etc.) modem and requires the modem to be variable regardless of the type of connection of the physical layer. A single modem should perform variable point IFFT/FFT in which various sizes of IFFT/FFTs are performed in order to perform a variety of modulation and demodulation functions in the IEEE 802 (11a, 16e, etc.) standard.